Process for the manufacture of rayon from viscose with high elongation and spooling in centrifugal cups



April 1, 1952 N. DRlscH ET AL 2,591,243 PROCESS FOR THR MANUFAOTURR ORRAYON FROM VISCOSE, WITH HIGH ELONGATION AND SPOOLING IN CENTRIFUGAL.CUPS Filed June 17, 1950 Snventors Patented Apr. 1, 1952 UNITED sTATEsPATENT 2,591,243 OFFICE PROCESS FOR THE MANUFACTURE OF RAYON FROMVISCOSE WITH HIGH ELONGATION AND SPOOLING IN CEN- TRIFUGAL CUPSApplication June 17, 1950, Serial No. 168,674 In France February 21,1947 4 Claims.

This invention relates to the spooling of rayon. In the manufacture ofrayon from viscose, the

latter is commonly spooled, after congelation, by

means of suitable devices, such as bobbins or centrifugal cups.

This application is a continuation-in-part of our co-pendingfapplicationSerial No. 9,115, nled February 18, 1948, for Process for theManufacture of Rayon-from Viscose, With High Elongation and Spooling inCentrifugal Cups, now abandoned.

In spinning .accompanied by spooling in centrifugal cups, the threadleaving the bath passes over at leastone feed roller which delivers itat a definite speed, e. g. of the order of 60 to 100 meters per minuteor more, whereupon the filament passes through a funnel into a rapidlyrevolving centrifugal cup. Owing to its mass, the filament is flungradially against the internal wall of the cup, and is wound up upon thiswall. The funnel performs suitable vertical reciproeating movements, asa result of which the lament and to transformation of the cakes intosecondary spoolings. the internal tensions referred to may proveprejudicial to proper formation of cakes and hence to the scientificmass production of rayon by these methods.

Attempts have been made to overcome the effect of these tensions by theapplication of a supplementary feed roller revolving at a lower speedthan the last feed roller proper, but this expedient, in addition tocomplicating the equipment, has proved only partially eective.

The present invention provides a process for obtaining dense, perfectlyuniform and heavy ment is' wound in intersecting helicoid spirals. l

This produces-ywhat is currently known as a filament cake, the thicknessof the cake being greater or less according to the duration of thespooling. When the cake attains a certain diameter it is removed fromthe cup and the operation is repeated.

The rapid rotation of the cup produces a torsion in the filament, thevalue of which depends in principle on the linear speed of the lamentand the number of turns in the cup. The magnitude of the centrifugalforce exerted upon the filament depends on the speed of rotation of thecup. the mass of the filament, and the radial travel of the filamentbetween the end of the funnel and the internal surface of the cake inSi".

process of formation. All other things being equal, this force decreasesas the thickness of the cake increases.

Now, when, f according to one of the many known processes. atension isapplied to the filament, whetl'lerin-Y the congelation bath, outside ofthe bath, or both, the feed roller (or the last feed roller if there areseveral) must theoretically overcome the resistance upstream and deliverfilament at a tension determined by the force of the centrifugal cup.However, such internal tensions as are created by stretching may persistand reduce the centrifugal effect in the cup, since the two forces actin opposite directions.

Since obviously the cake will be more compact the higher the centrifugaleffect, and since tightly packed cakes are desirable as affording longerperiods of spooling and hence more eilicient utilization of thematerial, apart from other advantages relating to subsequenttreatfilament increases.

filament cakes, e. g. 500,` to 600 grams, in conventional centrifugalcups.

This process is characterized by an extreme enlargement of the travel ofthe filament without stretching tension betweenthe point where thefilament reaches the last feed roller and the spinning funnel, such thatthe duration of this travel becomes at least 3 seconds.

Such a duration of this travel (under nonstretching condition) allowstime for the proaressive relief of internal stresses in the filament butwithout plastic deformation so that the filament loses the undesiredinternal tensions due to stretching before itis spooled, thus leavingthe effectiveness of the centrifugal force unimpaired. The inventionalso provides an apparatus for fabricating rayon filament and spoolingthe same in a centrifugal cup, such apparatus representing animprovement relative to the previous processes and being characterizedby comprising means for substantially enlarging the travel undernon-stretching tension between the last feed roller or rollers and thefunnel.

The travel between the point where the lament reaches the last feedroller and the funnel may, in pursuance to the invention, be increasedthree-, five-, or ten-fold, and more. This travel must be increased asthe linear speed of the suitable travel for a linear speed of meters, atleast 13.50 meters are required for a linear speed of 100 meters/min. sothat the time required for the filament to cover the distance betweenthe last feed roller and the funnel will be at least 3 seconds asaforesaid. ,y

The process may be applied with special advantage to spinning in bathscontaining more than 50% of sulfuric acid. The congelation of theviscose filament in a bath of at least 55% sulfuric acid is followed bysubjection to extreme stretching in the presence of such acid acting asa plastifler, or alternatively in a secondary bath e. g. on an aqueousbase at C. minimum. whereupon the filament is kept under non- If e. g.ten meters is the Y three seconds.

stretching tension between the last feed roller and the spooling meansfor a duration of at least This travel may include the time in the Washbath.

Through the combination of such' congelation bath with prolongedmaintenance under tension in air before fixation and spooling, filamentsare obtained with a tensile strength in grams denier of 4 or 5 and more,with ultimate elongations definitely above those obtained without suchprolonged aerial travel, namely of the order of 9 to l instead of 7 to 8per cent. The knot strength and loop strength are likewise improved byl0 to 20 per cent.

The invention is not confined to spooling in centrifuges, the sameimprovement in certain characteristics of the filament being obtainedwith any method of spooling, as e. g. on bobbins or spools.

The effect is probably connected with the phenomena of relaxation in thelament While kept under non-stretching tension over an extended travelduring a substantially longer time than that of the usual travel. Duringsuch a prolonged travel, the internal tensions are considerablyrelieved, and after shrinking of the gel in the aqueous wash bath, themolecular equilibrium is appreciably better than that of a filamentspooled immediately after drawing.

In the accompanying drawings, which are given only by way of example,

Fig. l is a schematic representation of the portion of an apparatusdesigned in pursuance to the invention included between the feed rollersand the centrifugal cup; and

Fig. 2 is a schematic representation of an apparatus according to theinvention including an acid bath and a wash bath between which thefilament is tensioned.

According to the example shown in Fig. l, the

filament 3, after passing over the feed rollers l and 2, describes azig-zag path as it passes over a series of guide means 4, 5, 6, 1 and B,before entering the funnel 9 of the centrifugal cup I0 where thefilament is spooled to form a cake H. The guide means 4 to 8 maycomprise pins, rollers, reels, etc. whose number may be varied accordingto the length of travel desired. The travel may be further increased byallowing the filament 3 to describe several helicoid spirals about theroller 2, and thereafter to follow a zig-zag course or any other deviouspath.

According to Fig. 2, the spinneret 2l is shown as immersed in a bath 22containing 975 grams of sulfuric acid per liter and having a temperatureof 20 C. The spinneret 23, having e. g. 1000 holes, is charged with asuitable volume of viscose at 6% of cellulose and 9% of soda, so thatthe resulting yarn runs 900 deniers for a spinning speed of 20 meters.The travel through the bath is to 60 centimeters in length. The filament3 passes over a guide roller 24 and is led over a feed roller 25, whenceit proceeds to the final feed roller 2. Between these two rollers,separated by about l meter, the filament 3 is drawn out 200%, reducingthe rating' to 300 deniers per thousand strands. The filament describesa certain number of parallel spirals (e. g. 10) ori a roller 2associated for the purpose with a rod 25 with axis slightly inclined tothat of the roller 2, for effecting automatic uniform spacing of thespirals. This winding in several spirals greatly increases cohesion andfacilitates uniform drawing. VOne or more Vcomplete spirals mayadditionally be wound on the roller 25 to 'improve traction on th'.roller also, and reduce slippage.

Subsequent to the extended path over the final roller 2, the lamentpasses through an aqueouswash bath 2l and then over a guide 8, whereuponit goes down through the funnel 9 and iscollected at il in the cup l0.The cup i0 may be replaced by other spooling means, as a bobbin or spool'if desired.

The path of travel between the last feed roller 2 of Fig. 2 through thebath 2l to the funnel is such as to provide the above mentioned threesecond dwell under non-stretching conditions before spooling.

In each case the entire stretching takes place prior. to the last feedroller 2 and the filament between the feed roller; 2 and the funnel 9 isunder only the non-stretching tension which is necessaryforfeedingpurposes and is produced by the centrifugal spooling action. Hence theinternal tensions are relieved before spooling and are not present tooppose the centrifugal force in the cup. A more compact cake is thusformed. 4

Although a specific embodiment has been shown for purposes ofillustration, the invention is not to be restricted thereto, but is tobe limited only in accordance with the scope of the following claims.

What is claimed is:

l. The method of making rayon lament from viscose which comprisesfeeding the rayon fila.- ment through a coagulating bath withoutstretching, removing the filament from the coagulating bath, thenstretching the filament at a stretchingstation and subsequently holdingthe stretched filament under non-stretching conditions for a period ofat least three seconds while conveying the stretched filament from thestretching station to a winding station so as to allow completerelaxation and relief of internal strains before winding and thenwinding the said filament.

2. The method of making rayon filament from l viscose which comprisesfeeding the rayon filament without stretching through a coagulating bathcontaining at least 55% sulfuric acid, removing the filament from thecoagulating bath, then stretching the filament at a stretching stationand subsequently holding the stretched filament under non-stretchingconditions for a period of atleast three seconds while conveying thestretched filament from the stretching station to a winding station soas to allow complete relaxation and relief of internal strains beforewinding, and then winding the said filament.

3. The method, as set forth in claim l, in which the extreme drawing iseffected prior. to washing and in the'presence of an acid. as aplasticizer.

4'. The method, as set forth in claim l, inY

y which-the extreme drawing is eected in an aqueous medium at about C.

, NICOLAS DRSCH. Y ROLAND BREPSON.

@REED The following references are of record in the file of this patent:Y

UNITED STATES PATENTS Number Name Y Date Re. 18,170 vf .ilienfeld T Aug.25, 1931 2,309,072V `Burkholder T Jan. 19,1943 2,348,415 Polak ug May 9;1944

